1. Field of the Invention
The present invention relates to an automatic gain control circuit for automatically controlling a gain of a gain control unit (below, preceding gain control unit) provided in a high frequency unit and the gain of a gain control unit (below, following gain control unit) provided in a low frequency unit. The present invention is advantageously applied to a wireless apparatus operated by a space diversity reception system with a CDMA (Code Division Multiple Access) method.
2. Description of the Related Art
As is known, in a wireless apparatus, a signal level at the reception of a receiver always fluctuates in the relatively large amplitude. This is because the propagation characteristics of radio wave fluctuates in accordance with the various propagation paths of the radio wave. In order to solve the problem of the fluctuation of the signal level at the reception of the receiver, an automatic gain control (AGC) circuit is usually provided in the wireless apparatus for amplifying or attenuating the signal level at the reception of the receiver to a necessary level. However, in general, conventional AGC circuits have large and complicated structures because two AGC circuits each having similar circuit structure are provided in the preceding and following gain control units. Accordingly, it is desired to simplify the structure of the AGC circuit.